1. Technical Field
The present disclosure generally relates to servicing a wellbore. More particularly, this disclosure relates to servicing a wellbore with calcium alumina cement compositions comprising a set retarding agent and methods of making and using same.
2. Background
Natural resources such as gas, oil, and water residing in a subterranean formation or zone are usually recovered by drilling a wellbore down to the subterranean formation while circulating a drilling fluid in the wellbore. After terminating the circulation of the drilling fluid, a string of pipe, e.g., casing, is run in the wellbore. The drilling fluid is then usually circulated downward through the interior of the pipe and upward through the annulus, which is located between the exterior of the pipe and the walls of the wellbore. Next, primary cementing is typically performed whereby a cement slurry is placed in the annulus and permitted to set into a hard mass (i.e., sheath) to thereby attach the string of pipe to the walls of the wellbore and seal the annulus. Subsequent secondary cementing operations may also be performed.
Wellbore servicing fluids are often modified to allow them to function for their intended purpose under extreme conditions (e.g., high temperatures/pressures, acidic environment). At high static subterranean temperatures, and in the presence of brines containing carbon dioxide, conventional hydraulic cements rapidly deteriorate due to alkali carbonation. Thus, the use of conventional hydraulic cement compositions in these types of environments may result in the loss of wellbore integrity. An alternative to conventional hydraulic cements when cementing in challenging environments such as steam injection wells or steam production wells is calcium aluminate based cement (CABC). The higher temperature resistance of CABC when compared to Portland cement/silica mixtures is an advantage for long term integrity of the cement sheath. The use of CABC offers many advantages as they provide in addition to high and low temperature resistance, resistance to sulfates, corrosion and sour gas. Additional examples of wellbore servicing operations that typically employ CABC include the servicing of geothermal wells or carbon dioxide injection wells. Calcium Aluminate Cements (CACs) combined with a soluble phosphate salt, for example sodium metaphosphate and a pozzolanic material such as Class F fly ash, form quick setting cement compositions that upon setting bind well to the subterranean formation and to itself and display desirable mechanical properties such as high strength, carbonation resistance, low permeability, and improved corrosion resistance.
A variety of CACs are commercially available with varying alumina contents. While attractive from an economic standpoint, one drawback to the use of CACs is their unpredictable thickening times. As such, the unpredictable thickening times of CAC slurries make well cementing with these types of cement a challenge. A need therefore exists for materials that can retard the CAC slurries so that the CAC slurry may display predictable thickening times and remain pumpable before they are placed into the desired location.